Electroplating is primarily used for depositing a layer of material to bestow a desired property (e.g., abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities) to a surface that otherwise lacks that property. Another application uses electroplating to build up thickness on undersized parts. The process used in electroplating is called electrodeposition.
Nickel is a silver-white metal that is electrodeposited onto surfaces in a variety of industries including the electronics, electroforming, and automotive markets. Bright nickel is mainly used for its decorative value because it offers a smooth and mirror bright finish. A drawback to bright nickel is that the brighter the deposit gets, the less ductile it becomes.
For example, one component of the space shuttle main engine is plated with nickel. Removal of impurities from the metal nickel plating chips in recent years (e.g., with the use of nickel purifiers (removes cobalt), water purifiers) is believed to be responsible for reduced strength in electrodeposited nickel.
When electrodeposition of nickel from a typical nickel sulfamate plating solution is done over many days and while plating large parts, deposited nickel with reduced mechanical properties may be deposited. As a result, plating must typically be terminated and the part removed until the plating solution is reconditioned. These interruptions create additional problems when plating resumes by requiring exacting surface preparation procedures to ensure the subsequent nickel layers bond adequately. In addition, each additional plating cycle increases fabrication time and production costs. Therefore, it is desirable to reduce the number of plating runs, thereby resulting in cost savings and a better part with fewer bondlines.
The introduction of cobalt into the deposition of nickel to increase strength is known in the art. Conventional systems and methods typically use cobalt levels greater than 10%. However, a deposit containing 10% cobalt is too brittle for structural applications and results in a part that is not readily weldable. Conventional systems typically utilize cobalt concentrations greater than 1% as well as utilize other metals and/or organic additives in the plating solution. The concentration of cobalt utilized may be product or application specific and/or may be specified by the customer. For example, a customer may specify the alloy content and the plating company would adjust its plating tank accordingly.
The need remains to provide a simple and cost-efficient nickel sulfamate plating system that does not require brighteners, unusual additives, or other metal constituents to electrodeposit a nickel-cobalt alloy with increased tensile strength and low sulfur content. The low sulfur content allows the alloy to be welded increasing the number of potential usages.